Traditional incandescent lamps have issues of high power consumption and short lifetime. The invention of light emitting diode (LED) solved the power consumption and lifetime issues. It is also expected to be a mainstream light source in the future. LED lighting is recently commercialized and aggressively taking market share.
An LED is a directional light source with high brightness. Therefore, diffusers are required to distribute light into a desired uniform light output and to provide sufficient overall brightness in a space without hot spots. A diffuser also prevents the discomfort of staring directly at the lighting device. Diffusers are frequently made of polymer resin with particles of various refraction indices to create the diffusing effect through light scattering. In order to simultaneously achieve the high total brightness and uniform lighting performance, diffusers with surface optical patterns are usually used. In addition, integration of a surface patterned diffuser with a light guide can make for the very flexible design of lighting devices.
In addition to a uniformity requirement of LED-based lights, there is also a need for artistic presentation.